I've had this lens for one year now and have taken 1000's of photos with it and they never seem to dissapoint me. I've used this lens for many situations and it always seems to handle anything I do. I had a Sigma 70-200 f/2.8 EX before this and I was very pleased with the quality of that lens, but IS was just too valuable for me. I do not regret the decision one bit. I can honestly say this lens will NEVER be sold!

My first test shots were at 200mm, f/2.8, at a 15th and they were tack sharp. I was worried about the IQ at 2.8, but after shooting just a few pics wide open I never second judge this lens. I've used a Sigma 1.4 EX teleconverter on this lens with outstanding results.

Lens hood. Shooting a 20d with the pop-up flash will produce a shadow.
Not quite the build quality as others, but for less money it's on par.

I set out looking for a wide angle zoom lens only to find that the choices were limited and expensive. The Canon 16-35 was way too much, the 17-40 was getting close to my price range, but for the amount I use a wide angle I couldn't justify the price.

I already use the Tamron 28-75 XR Di lens with great results so I decided to try the little brother version (the 17-35). I found one used on this board for 440.00 with a B&W UV filter and couldn't be happier with the pictures I'm getting. I typically stay at around f/4 to f/8 but am not afraid to stop down to f/2.8 when possible.

I would say that f/2.8 might be a tad soft compared to f/4-f/8, but not so much that it's going to stand out in pictures.

I did do some tough lighting shots where glare could've been a problem, but I was very happy to see none.

I would say if wide angle is not your specialty and this lens would not be on your camera the majority of the time then it's a no brainer (buy one). If you are trying to sell wide angle photos as a professional then there might be better choices, but they are also going to cost much more.

This lens for the price is very pleasing. A good friend of mine that is a well respected professional told me about this lens after he used it next to his 24-70L and was finding it difficult to pic out the differences. If you can put your ego to the side and not worry about shooting something other than a Canon L series, you'll be happy.

Cons:

For the price, NONE.

It's hard to say something bad about this lens considering the price. If you compared to the 24-70 L lens you might find the auto focus to be a tad bit slower, but either way the lens still focuses faster than I can so I'm happy with it. I see alot of people putting it down but I truely think they can't come to grip with a 350-400$ lens being so very close to their 1,100$ lens. Put the ego aside and start shooting, you'll be surprised!